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Discussion in 'GT6 Tuning' started by DolHaus, Jan 16, 2014.
Testing the class are you?
Just checking you were paying attention at the back
Missed one thing, the isometric exhaust manifold do not increase max RPM, it's the only power part on the left side that do not add RPM.
I knew there was one part on the left that didn't add RPM but I couldn't remember which, thanks for clarifying
Hey @LionHeart, @Ridox, very fast guys looking for mistakes, remember me don't race against you
I changed to SS tyres and added some power parts to reach 600PP. I got it by different ways, using more or less power limiter depending on case:
Red line: 7500rpm
Max Power: 6400rpm
Max Torque (867Nm): 4500rpm
Red line: 7400rpm
Max Power: 6500rpm
Max Torque (859Nm): 4400rpm
Red line: 7300rpm
Max Power: 6800rpm
Max Torque (851Nm): 4300rpm
In the first case we have a flat power curve due to the power limiter, on the second the “flat zone” is smaller, and in the third, the power curve is very sharp. As we increase the power, the torque decreases.
I’m going to test the three options to know if I’m able to detect the differences although they are very small and they are going to be hidden in a poor driving style. Which one do you recommend me the higher torque and bigger power band?
Because we are tuning for a relatively high speed circuit with very few low speed corners I would expect option 3 to perform best. You will utilise more of the power band during the lap than the torque band so it makes sense to lean towards that side of things, if we were tuning at a lower speed track where you need to get the car to accelerate harder out of slow corners then I might lean more towards a torque focussed build
Excuse me for disappearing, I’ve been very “busy” with my children last week and I haven’t been able to invest much time on the Corvette, but wow!!! at first sight I’ve realized it’s not a Miata
I’ve only test the LSD trying to control the car without reducing very much the Accel. value, I’m using 10/15/20 like I told you, and I don’t know, I have to be very cautious with the throttle, if not, the tail tries to overcome and I lose the control.
On the other hand, I have to reduce a bit the Decel. value, cause when I brake it’s like a brick, doesn’t turn and goes straight.
I hope to be able to practice more this week and improve bit to bit… Can I start the process in the same way as with the Miata: LSD, ARBs, spring rate, ...?
No worries, I'm quite happy to proceed at what ever speed works for you
We will be proceeding slightly differently than we did with the Miata because of the use of the spring rate calculations but as always we will be targeting the largest issues first. In this instance the largest issue is likely to be power application as we are trying to put 700hp through the rear wheels which is always going to cause problems.
When the car is losing control during throttle application which rear wheel is turning red first? Sounds like you've got the hang of adjusting the Decel so feel free to adjust that as you see fit. We don't need the LSD to be perfect at this stage as we will be changing the amount of grip available when we adjust the spring rates but we need to make it as manageable and predictable as possible to aid us in spotting other problems/improvements. Chances are that it's always going to be a bit of a handful on corner exit but we want the behaviour to be predictable so we can use our skill as a driver to avoid problems such as wheel spin and oversteer.
The first wheel that turn red is the exterior, that’s why I say I have to reduce the Accel. value, but I didn’t like to reduce it very much to improve my driving style and to learn to control the car by myself.
Finally I drove the car several laps and I felt the following:
Initially, with LSD 10/15/20, the car was a brick, it still straight after release brakes regardless the wheel’s angle. I thank it was because I broke too late, but it was the same braking earlier. Then I reduce to 7 the Initial. Why 3 points? I don’t know, but now it works, I have to try 8 and 9 to see how it goes.
Like the car continue oversteering when throttle, I reduced the Accel. value to 12, It’s not perfect but it’s obviously better and, like I say earlier, I like to improve, and it’s not possible with 100% of confort.
I think I could reduce the Decel. value too, is the next parameter I like to review. The car brakes well, but if it would slides a little I think it would help to trace better the bend.
Like you say, it’s the first step into LSD, it hasn’t to be perfect now. My current values are 7/12/20.
Something that I’m feeling now inside a bend is that although the car seems to go by the right path (I haven’t smoke nor red rear tyres, only the same as always, the orange front exterior tyre), I feel all the wheels slide, it’s not understeer, it’s not oversteer, the car turns but it needs wider road by the exterior of the bend… I don’t know if I’m able to explain myself correctly.
The car feeling like a brick under braking is a result of the Decel being to high, you should be reducing that first before messing around with the Initial because the Inintial affects both Accel and Decel so while you might be solving one problem you could be unintentionally creating another. There is nothing wrong with adjusting the Initial but it can cause problems if adjusted incorrectly.
With the Accel you want to keep reducing it until the inside wheel starts lighting up under acceleration, you are looking for the point of failure so you know where the limits are. Once you find the point where the inside wheel starts spinning you can then increase the number by 1 or 2 clicks, there is no point in making it harder to put the power down than it needs to be, nothing kills performance like not being able to use the power so if you can get it to the stage where you can just mash the throttle and power out of a corner then that will always be in your favour.
As for this issue I'm not sure what you are trying to describe, the only way you'll get all four wheels sliding is by chucking the car into the corner far too fast on entry, during corner exit you will only ever get oversteer or understeer with a RWD car (you could get a 4-wheel drift going in a 4WD but it takes a fairly specialised setup). Which corner are you having this problem on?
Just thought I'd add a map to make sure we're referring to the same corners
Hey, thank you. I also had an image ready to send it to you … an image is worth a thousand words. I felt it on bends 2 and 6. I’m racing on the clockwise direction: 1, 2, 3… to 17.
Yes, you’re right, I’m confusing concepts, and the problem is understeer on corner exit. The car’s tends to go to grass on the outside of the corner.
I was convinced that the problems I had was related to the LSD Initial phase (when I release the brakes and before push the throttle again), but now I realize they started as a consecuence of LSD Decel. phase. I decreased it a bit and the things start to go better.
Changing subject, you tell me to reduce the Accel. until the inside tyre goes to orange, but… is it always the best choice, aren’t we loosing too much acceleration power, or by two or three ticks there is not much difference and we win stability?
I'm going to test the car tonight, tomorrow I'll post you my new configuration.
If the car feels like it is understeering or feeling unresponsive during the neutral phase after you lift off the brakes then the Initial could indeed be too high so you are right to lower it but it is important to focus on one problem at a time and the way you described it sounded more like a Decel related problem. My advice would be to concentrate on the Decel first as it give much clearer indicators than adjustments to the Initial, once the braking is sorted then start making adjustments to the Initial and note the changes
In terms of losing acceleration power by reducing accel we are only talking about minuscule amounts so there is very little cause for concern, being able to accelerate earlier out of a corner will always give better results than the efficiency of power delivery. I would much rather that the Accel was a little bit too low than a little bit too high as it has less of an effect on the overall ability of the car, as long as you're not spinning the inside wheel out of tight corners thats good enough for the time being and we can fine tune it later.
If the accel is too high it prevents the car from following as tight of a radius during acceleration which presents itself as understeer during a tight corner exit, we could easily mistake this as being a problem with the suspension or wheel alignment and waste hours adjusting the wrong parts trying to fix an unrelated issue. Basically its easier to spot a problem with the Accel being too low than too high so we lean towards the lower end of the scale until we need to refine it at a later stage
To simplify further, a lower the number means more rotation is possible during that particular phase. Our aim is to maximise rotation without becoming unstable (Initial/Decel) or inefficient (Accel)
Just a quick couple of questions @speedy turtle , as I don't want to disrupt the class.
Do you have a rear spoiler?
Is your End Final above 30% of its range?
Example: Final Gear range = 2.000 - 5.000 and Final Gear is set at 3.500 (which would be 50% of the slider)
I will add that trying to tame this 600pp beast on Sports:Soft, at this track, is not an easy challenge. Ok I'll shut up now.
I can't tune a transmission by proxy so we're avoiding the subject as much as possible
Oh I totally understand staying away from transmissions. It was more for my notes, as I'm sure you'll tune around it.
This is standard info, so 99% of anyone who see's this already knows this, but ;
The final gear is always dependant on the longest straight, and really is the only part that has almost nothing to do with the tune itself.
That said, on the X track (the 20 million mile oval track) has those painted lines on it. Between the gauges and just simply reading the "longest straight" info on whatever track your tuning for, you can estimate and adjust on the X track your final pretty easily. After doing this with a few tunes, you begin to get used to and remember each tracks roundabout lines, so you don't have to keep checking back and forth.
Its also a good spot to adjust straight line braking, and make mental notes on distance.
Thats how/where I usually adjust the final, I thought it might be an idea others could use/try, hence why I posted this.
Of course, your eventually going to be on the track your going to race on, and readjust there. But except for seasonal tuning, I really don't like tuning cars specifically for only 1 track. Again, hence this post, lol.
Fair enough, I remember the C6 being a good work horse at 600pp, not the fastest but reasonably easy to control. We will be discussing the relevant changes in terms of suspension tuning when considering a spoiler soon, I don't believe it has been fitted yet though
In a basic sense you are right in that the final gears main function is adjusting top speed but it can have a noticeable effect on the handling as well. I can't remember off the top of my head exactly how it works but you can either stabilise or free up some rotation by tuning the transmission in a specific way, the other thing is the difference between long a short gears having a fairly pronounced effect on power delivery particularly out of slow corners and therefore your LSD settings. Try doing a reverse transmission flip (max speed to the right/final to the left) and compare the difference, I can't remember the approach I was using towards the end but that's how I stumbled across it and just continued playing around from there.
When it comes to tuning to suit straight length I noticed a fairly common mistake that people tend to make, a lot of people seem to aim to be just shy of the rev limiter by the end of the straight and although its not a bad method there is a slightly more efficient route. We need to take into consideration the power band of the car first and foremost because on every engine there is always a decline in power output at the top of the RPM range, a basic point of physics is that the faster you go the more energy you need to keep accelerating so why would we want to be using less than peak power when we need it most? Instead of ending up near the rev limiter at the end of the straight we want to be just past the peak to ensure we are utilising the power efficiently. It might only make a few mph difference and it's not applicable in every instance but every little helps
Can I get in on this? I'm bored in GT until I get my wheel and want a project
You are welcome to ask any questions you may have
So what're you guys trying to fix? A Vette tune?
We're not trying to fix anything, just teaching someone the tuning process from start to finish so they can apply it to any car in future
Ah. I'll help, even though I'm not the best tuner. Turns out that problem with my driftcar a while back was my incredibly bad tuning. Who'd've (yes that's a word) thunk it.
You are welcome to follow along and ask questions but I'd rather avoid too many cooks spoiling the broth
Thank you for your contribution @LionHeart, I appreciate any kind of help comments. I’m open to anything allows me to improve.
I didn’t add any kind of spoiler nor configure the gearbox yet. You’re reading the thread, by now we are starting with the Corvette, and like the Miata we start with a total standard car, only “added” the weight reduction and those parts that you can add or substract but not configure: carbon shaft, twin plate clutch, … no ballast, no spoiler.
Please don’t stay quiet, you can talk whenever you want… with the permission of DolHaus, of course
Finally yesterday I was able to race a bit. I configure the car with LSD 9/10/15, it’s not perfect, but being a little careful with the throttle I can control it.
Accel. 10 is the point at which I find balance getting red both rear tires, more or less at a time.
Decel. 15…. I raced several laps with this value at 12 and I thank it was ok, it was on the edge between the stability and the initial sliding rear axis, then I reduced to 10 and I realized I have to be very careful. Finally, I test with 15 and I made my best time for now…
Initial 9, I don’t know what to say… when I lift the throttle while turning, the rear axis slides a bit, nothing annoying, on the contrary, permits to align the car looking for easier corner trace.
Yes, we are leaving the gearbox to the final… I think the car reactions can be improved yet without configuring the gearbox at this point. I feel the car more manageable than the Pozzi RS, not being essential its tame using the gearbox, but if you think it could help...
@speedy turtle if you don't mind....
What lap times are you currently running at with your changes?
What were the lap times when you first started?
If you don't care to share your lap times, I understand. I was just thinking that it might assist @DolHaus in determining your driving ability and style.
From the sounds of it, you are getting more comfortable with the car, so if there isn't much improvement in lap times, don't worry about it. Comfort leads to confidence and that, in itself, can make for better driving.
That was very well said. ^^
Yes, no problem. I have much to learn yet and any help is welcome:
Circuit: Grand Valley
Car: Chovrolet Corvette ZR1 (C6) '09
Initially, with the stock car (only weight reduction applied) and LSD on values 10/40/20: 2:05.xxx
With the first LSD configuration (10/15/20): 1:55.660
With the current configuration (9/10/15): 1:53.429
Like you've read we haven't modify the suspension, we have much work to do yet.
Talking about my skills, very modest yet. I've done the following in the new time trials:
Car: Tommykaira ZZII
Time to gold: 1:21.000
Time done: 1:19.500 (1:18.457, two minutes ago )
Car: Toyota TS 030
Time to gold: 1:30.000
Time done: 1:24.094
Too far from the bests yet, but several months ago I wasn't able to make lap times only 10 seconds slower than the best in the world ranking, and now I'm "only" 6 or 7 seconds slower... it's an improve.
Ok great, sounds like the LSD is more or less where it needs to be so we can now begin to adjust the suspension balance in order to maximise grip and rotation.
(copy and pasted from a few pages back, if the details have changed please let me know)
Chevrolet Corvette ZR1 (C6) ‘09
Weight: 1206 kg
Weight Distribution: 49:51
Suspension: (All standard values)
Ride Height: Front: 80 Rear: 80
Spring Rate: Front: 11’14 kg Rear: 12’77 kg
We will be using the equation we discussed earlier ((Weight X Gravity) X Weight Distribution) to find a starting point and then we can personalise it from there.
I will be first looking to match the default front spring rate as closely as possible:
(1206 X 9.81 = 11830.86) x 0.49 = 5797.1214 - we shall refer to this number as C from now on
C represented as a spring rate would be 5.80kgfm so we can make a rough guess at how much we need to multiply it by to match our default front spring rate (11.14kgfm)
(numbers simplified/rounded up to save typing)
C X 1.5 = 8695 ---- Too low
C X 1.6 = 9275 ---- Too low
C X 1.7 = 9855 ---- Too low
C X 1.8 = 10434 ---- Too low
C X 1.9 = 11014
C X 2 = 11594 ---- Too high
Change front spring rate to 11.01kgfm
We can now set our rear springs using the same multiplication factor and begin testing this setup shall be referred to as "Balanced Numbers Setup"
(1206 X 9.81 = 11830.86) x 0.51 = 6033.7386 = C
C X 1.9 = 11464
Set rear spring rate to 11.46kgfm and take the car for a test drive. You'll want to spend a good few laps getting to know this setup, concentrate on how much grip it has in all the main areas - how well does it brake? how well does it rotate? How well does it put the power down on exit?
Please give feedback on your experiences and we will begin to modify from there, it seems a little bit complicated at first but you should hopefully get the hang of it. Please tell me if the weight mentioned is correct, if it isn't then maybe it would be a good practice for you to change the relevant parts in the equation and show your workings. (another useful bit of information would be how close the little blue bars are to equal, if they look fairly close then don't worry about it but please tell me if they look unbalanced)
I have adjusted the transmission... I have yet to tune the LSD (mine is set at what I call "default" for RWDs 10/20/20); but those numbers that you have for your current configuration sounds very close to what I would come up with.
1:49.9xx and looking forward to tuning the springs.